Electrophotographic member



United States Patent ELECTROPHOTOGRAPHIC MEMBER Wilhelm Neugebauer,Martha Tomanek, and Hans Behmenburg, all of Wiesbaden-Biebrich, Germany,as-

s gnors, by mesne assignments, to Azoplate Corporatron, Murray Hill,NJ., a'corporation of New Jersey No Draw1ng. Filed June 3, 1957, Ser.No. 662,981

Claims priority, application Germany June 2.7, 1956 52 Claims. (Cl.96-1) This invention relates to photographic reproduction and moreparticularly to electrophotographic processes, namely processes in whichan electrostatic latent image is produced by utilizing the property ofphotoconduction (i.e. a variable conductivity dependent on the intensityof illumination). The electrostatic latent image may be produced in aconventional exposure operation, for example by means of alens-projected image or by contactprmting techniques, whereby anon-visible electrostatic charge pattern (the so-called electrostaticlatent image) is created on a surface. In this pattern the chargedensity at any point is related to the intensity of illuminationobtaining at that point during the exposure. The latent image may bedevelopedi.e. rendered visible-by means of an electroscopic powder, suchas a colored synthetic resin powder, and the resulting visible image maybe fixed by rendering the powder permanently adherent to a support onwhich the image is desired, for example in suitable cases by heating tosoften or melt the powder particles and/or the surface of the imagesupport, or by application of an electric field, or with volatilesolvents.

In electrophotographic processes the electrostatic latent image iscommonly formed on the surface of a photoconductive insulating layercarried on a support. For example, material comprising such support andphotoconductive layer may be sensitized by applying a uniform surfacecharge to the free surface of the photoconductive layer, for example, bymeans of a corona discharge, which charge is retained owing to thesubstantial insulating character, i.e. the low conductivity, of thelayer in the dark. On exposure, as described above, the photoconductiveproperty of the layer causes an increase in conductivity in theilluminated areas to an extent which is directly proportional to theintensity of illumination. As a result, the surface charge in theilluminated areas leaks away while the charge in the unilluminated areasremains. This result constitutes the aforementioned charge pattern orelectrostatic latent image.

Electrophotographic processes have become of increasing importance inrecent years, especially, for example, in connection with officeduplicating, where offering as they do a wholly dry copying process,they are greatly preferred. Much interest has been aroused and much workhas been done in this field, particularly in respect to obtainingsuitable materials for forming a support as well as for forming aphotoconductive insulating layer on the support. Although many effortshave been made to obtain materials capable of fulfilling modernrequirements in respect to range of use, reliability, simplicity inhandling, potential light sensitivity and keeping qualities, none hasproved adequate. Among photoconductive substances used hitherto,selenium has been the most notable; however, it too does not meet therequired standards.

The present invention has solved the above problems 3,112,197 PatentedNov. 26, 1963 and provides a material for use in electrophotographicprocesses which is capable of being rendered light sensitive by applyingan electrostatic charge thereto. It comprises a support carrying aphotoconductive insulating layer, which layer includes at least onephotoconductive substance consisting of a2,5-bis-(p-amino-phenyl)-1,3,4- triazole compound.

According to preferred embodiments of the invention, the photoconductivesubstances are of general formulae R represents a hydrogen atom or analkyl, cycloalkyl or acetyl radical,

R represents an alkyl or acetyl radical, and

R represents a hydrogen atom or an alkyl radical.

These general formulae include, for example, 2,5-bis[4'- amino-phenyl-(1') -1,3,4-triazole, 2,5-bis- [4-monoalkylamino-phenyl- 1)-l,3,4-triazoles, 2,5-bis- [4'-monoacetylamino phenyl (1')] 1,3,4triazoles, 2,5 bis [4'- monoacetylamino-phenyl-(1')]-1,3,4-triazoles,and also 2,5-bis[4-amino-phenyl-(l')]-1,3,4-triazoles in which thehydrogen atom in the l-position is substituted by an alkyl radical.

The 2,5-bis-(p-aminophenyl)-1,3,4-triazole compounds have very goodphotoconductivity and are particularly suitable for the preparation ofhomogeneous layers having very long shelf-life. The compounds arecolorless and fluoresce in daylight or in ultraviolet light.

The photoconductive substances are preferably applied to the support inthe form of solutions in organic solvents, such as for example benzene,acetone, methylene chloride, or glycol monomethyl ether. Mixtures of twoor more of the 1,3,4-triazole substances of this series in such solutionmay be used. Mixtures of solvents may also be used. Among the organicsolvents are, for example, benzene, acetone, methylene chloride andglycol-monomethyl-ether. Mixtures" of two or more photoconductivesubstances and mixtures of solvents may also be used. It is alsopossible to employ the photoconductive substances in association withother organic photoconductive substances.

It has further been found advantageous in preparing the photoconductiveinsulating layers to use the photoconductive substance or substances inassociation with a resin, synthetic polymer or other organic colloid,for example (a) Natural and synthetic resins, e.g. balsam resins, phenolresins and other resins modified with colophony, coumarone resins andindene resins and the substances covered by the collective termsynthetic lacquer resins, which includes processed natural substancessuch as cellulose ether, see the Kunststoiftaschenbuch 3 (PlasticsPocket Book), published by Saechtling-Zebrowski (11th edition, 1955,page 212 onwards);

(b) Polymers (including co-polymers) such as the polyvinyl chlorides,polyvinyl acetate, polyvinyl acetals, polyvinyl alcohols, polyvinylethers, polyacrylic and polymethacrylic esters, and polystyrene andisobutylene polymers;

(c) Polycondensates, e.g. polyesters, such as phthalate resins, alkydresins, maleic acid resins, colophony esters of mixed higher alcohols,phenol-formaldehyde resins, particularly colophony-modifiedphenol-formaldehyde condensates, urea-formaldehyde resins,melamine-formaldehyde condensates, aldehyde resins, ketone resins ofwhich particular mention is to be made of AW2 resins of the firmBadische Anilinund Sodafabrik, xylene-formaldehyde resins andpolyamides; and (d) Polyadducts, such as polyurethanes.

4 solutions of polyamides in aqueous alcohols. Aqueous dispersions ofother substances suitable for the pretreatment of the paper surface mayalso be used.

Solutions of the photoconductive substances in organic solvents asdescribed above, with or without the added organic colloidsaforementioned, can be applied to the supports in known manner (forexample, by spraying, direct application, or whirl coating), and thesupports thus coated, dried, so that an even photoconductive layer isformed thereon.

While the layers are, in themselves, non-light-sensitive, by applying apositive or negative electrostatic charge thereto, by means, forexample, of a corona discharge, the layers are rendered light-sensitiveand can be used with long-wave UV. light of 3,600 to 4,000 A.U. inproducing electrostatic latent images as described above. Very goodimages may be obtained by a short exposure under a master to ahigh-pressure lamp.

Although the layers when charged are but slightly sensitive to light inthe visible spectrum, it has further been found that their spectralsensitivity can be extended into the visible part of the spectrum by theaddition to the layers of sensitizers, preferably in the proportion oneto three percent weight for weight of photoconductive substance. Themost suitable sensitizers are dyestuff compounds, a number of which aregiven by way of example in the following table:

Dyestufi Group Triarylmethane dyes Xanthene dyes:

Rhodamines Phthaleins Thiazine dyes Acridine dyes Quinoliue dyes Quinonedyestufi's:

Anthraquinones Cyanine dyes parent colourless layers on drying that canbe considered as solid solutions.

The support may be of any material suitable for use 65 inelectrophotographic processes, for example, aluminium or other metalplates or foils, glass plates, paper sheets or webs, or plastic foil,especially foils made of electrically conductive resins. If paper is tobe used as a support for the photoconductive layer, it is preferablethat it shall have been pretreated against penetration by the coatingsolution, for example, with methyl-cellulose in aqueous solution;polyvinyl alcohol in aqueous solution; a solution in acetone andmethyl-ethyl-ketone of a mixed poly- Reference (Sehultz DyestufiCompound Farbstofitabelien,

7th ed., Vol. 1 (1931).)

Brilliant Green No. 760 (p. 314). Victoria Blue B-.. 822 (p. 347).Methyl Vio1et- 783 (p. 327). Crystal Violet..- 785 (p 329). Acid Violet6B 8 351).

Rhodamine B No 864 (p. 365). Rhodamine 6G No 866 (p. 360). Rhodarnine Gextra No 865 (p. 366). Sulphorhodnrnine B No 863 (p. 364). True acidEosin G No 870 (I). 368).

Eosin S No 383 (p 375). Eosin A... No 881 (p 374). Erythrosin. No 886 (p370). Phloxin No 800 378). Rose Bengel No 889 (p '8). Fluorcscein No 880(p 373).

Methylene Blue No. 1038 (p. 449).

Acridine ye1low 901 (p. 383). Acridine orange--. 908 (p. 387).Trypaflavine N o. 906 (p. 386).

Pinaeyanol No. 924 (p. 396). Cryptocyanine No. 927 (p. 397).

Alizarin No. 1141 (p. 499). Alizarin red S No. 1145 (p. 502;.Quinizarine No. 1148 (p. 504

i f H1O C=GHCH=O1I-C CH1 CH: HaC ol-CH:

The layer-carrying supports may be utilized for the production of imagesby electrophotographic means, for example, as follows: When thephotoconductive layer has been charged, by means of, for example, acorona discharge with a charging apparatus maintained at 6000 volts, thethus sensitized layer is exposed to light under a master or by episcopicor diascopic projection and is then dusted over in known manner with asuitable developing agent such as a resin powder colored with carbonblack. We prefer a resin developer obtained by fusing 30 parts by weightof polystyrene (K-Wert 55), 30 parts by weight of a maletic acid resinmodified with rosin and sold under mer of acrylic acid methyl ester andacrylonitrile; or with 75 the registered trademark Beckacite K-lOS, and30 parts by weight or carbon black, and subsequently finely grinding thefused mass. The image that now becomes visible can easily be wiped off,and therefore needs to be fixed; it can, for example, be heated brieflyto approximately 120 C. by means of an infrared radiator. Thetemperature need not be as high as this if the heat treatment is carriedout in the presence of vapors of solvents such as trichloroethylene,carbon tetrachloride or ethyl alcohol. The powdered image can also befixed by means of steam. From positive masters, positive images of goodcontrast are produced.

After being fixed, these electrophotographic images can be convertedinto printing plates; the support, e.g. the paper or plastic foil, iswiped over with a solvent for the photoconductive layer, e.g. alcohol,or acetic acid and then rinsed with water and rubbed in with greasy inkin known manner. In this way positive printing plates are obtained whichcan be set up in an oflset machine and used for printing. They give verylong runs.

If transparent supports are used, the electrophotographic images canalso be used as masters for the production of further copies of any sortof light-sensitive sheets. In this respect, the photoconductivecompounds to be used, as provided by the invention, are superior tosubstances used hitherto, such as selenium or zinc oxide, inasmuch asthe latter give cloudy layers because solid solutions cannot be producedwith such materials and only suspensions are possible.

Where translucent supports are used for photoconductive layers such asare provided by the invention, reflex images can also be produced. Thepossibility of a reflex copy is also an advantage over the known art.

Moveover, the photoconductive layers prepared as provided in theinvention have a further important advantage in that they can be chargedpositively as well as negatively. With positive charging the images areparticularly good while there is negligible evolution of ozone, which isinjurious to health and is very considerable with negative charging.

The 2,5-bis [4'-aminophenyl-(1)] 1,3,4 triazole compounds correspondingto the aforementioned general formulae may generally be prepared asfollows: The corresponding 2,5-bis- [4-amino-phenyl-( 1')]-l,3,4-oxadiazole compound is submitted to prolonged heating withformamide in the proportion of about 100 g. of formamide to g. of theoxadiazole compound to temperatures of 180 to 190 C.; the reactionmixture is then poured into water, whereupon a precipitate is formed,which is separated by filtration from the mother liquor. The yield ofthe triazole compound is almost quantitative.

The 1,3,4-oxadiazole compounds used as starting material as describedabove in preparing the 1,3,4-triazolc compounds may themselves beprepared in manner known per se from 2 mol. of a correspondingp-aminobenzene-carboxylic acid and 1 mol. of a hydrazine salt, by meansof prolonged heating in the presence of a dehydrating agent. Thepreparation of the respective oxadiazole compounds has been set forth inFrench Patent No. 1,080,107.

If the oxadiazoles which are used as starting materials containnon-substituted hydrogen atoms in the two amino groups, formylationtakes place at these points. If the N-formylamino-phenyl 1,3,4 triazolesso obtained are boiled with 10% hydrochloric acid, hydrolysis of theformyl groups occurs and the required2,5-bis(aminophenyl)-l,3,4-triazoles with primary or secondary aminogroups can be obtained by neutralizing the hydrochloride solution withsodium hydroxide.

To substitute the hydrogen atom in the 1-position of the 1,3,4-triazolecompounds, by an alkyl radical, the starting triazole may be dissolvedin an aqueous alcoholic solution of caustic alkali and submitted to theaction of the corresponding dialkyl sulfate.

Examples of 1,3,4-triazole compounds which may .be

used according to the invention as photoconductive substances are asfollows:

7 compound, is separated by suction from the mother liquor, and thenboiled for one hour with hydrochloric acid. The formyl groups arethereby hydrolyzed. The acid solution is neutralized with sodiumhydroxide to produce the amino compound. The amino compound is purifiedby recrystallization from 80% ethyl alcohol.

2,5 bis [4 N,N diethylamino phenyl-(1')]-1,3,4- triazole correspondingto Formula 2 (melting point 198- 200 C.) may be prepared from2,5-bis-[4'-diethylaminophenyl-(1)]-1,3,4-oxadiazole, by heating for 12hours at 180l90 C. with ten times its weight of formamide. The reactionproduct is poured into water to form a precipitate which is dried andpurified by recrystallization from a benzene/ petroleum ether mixture.

2,5 bis [4 N,N dimethylamino phenyl (1')]- l,3,4-triazole correspondingto Formula 3 (melting point 255-256 C.) can be prepared in analogousmanner to the compound corresponding to Formula 2, by boiling 2,5- bis[4 N,N dimethylamino phenyl (1')] 1,3,4- oxadiazole, for 10 hours withten times its weight of formamide. The compound is purified byrecrystallization from 96% ethyl alcohol.

2,5 bis [4 N ethylamino phenyl (1')] 1,3,4- triazole corresponding toFormula 4 (melting point 168- 170 C.) may be prepared from2,5-bis-[4'-N-ethylaminophenyl-(1)]-1,3,4-oxadiazole, by heating atISO-190 C. with ten times its amount by weight of formamide. Thecompound thus produced is 2,5-bis-[4-(N-formyl-ethylamino)-phenyl-(1)]-l,3,4-triazole. Two hours boiling of this reaction product boiled fortwo hours with 10% hydrochloric acid to hydrolyze the formyl groups, andthe compound corresponding to Formula 4 is precipitated from thehydrochloride solution by means of sodium hydroxide.

1 ethyl 2,5 bis [4 N,N dimethylamino phenyl- (1')]-1,3,4-triazolecorresponding to Formula 5 (melting point 131 C.) can be prepared bydissolving 30 g. of the compound corresponding to Formula 3 in aqueousalcoholic potassium hydroxide and reacting the resulting solution withg. of diethyl sulfate for two hours at 60 C. When the reaction iscomplete, the reaction mixture is diluted with water. The precipitateformed is separated by suction from the mother liquor, washed in waterand recrystallized from 96% ethyl alcohol.

1 methyl 2,5 bis [4' N,N diethylamino phenyl- (1)]-1,3,4-triazolecorresponding to Formula 6 (melting point 132-133 C.) can be prepared inanalogous manner to the compound corresponding to Formula 5, bymethylating 36 g. of the triazole compound corresponding to Formula 2,at 60 C. with 15 g. of dimethyl sulfate in aqueous alcoholic potassiumhydroxide.

2,5 bis [4' (N acetyl amino) phenyl (1')] 1, 3,4-triazole correspondingto Formula 7; this compound does not melt below 300 C. and can beprepared by boiling g. of the compound corresponding to Formula 1 forthree hours with 250 g. of acetic anhydride. The reaction mixture ispoured into water, the liquid is filtered off, and the residue2,5-bis-[4'-(N-acetyl-amino)-phenyl- (1')]-1,3,4-triazole is washed withwater and recrystallized from 96% ethyl alcohol.

2,5 bis [4 N,N di n propyl amino phenyl- (1')]-1,3,4-triazolecorresponding to Formula 8 (melting point l96-l99 C.) can be prepared byboiling 2,5-bis-[4- N,N-di-n-propyl-amino-phenyl-(1) ]-l,3,4-oxadiazole,for six hours with ten times its weight of formamide. The reactionproduct is recrystallized from 96% ethyl alcohol.

2,5 bis [4 N ethyl N n propyl amino phenyl-(1)]-1,3,4-triazo1ecorresponding to Formula 9 (melting point 119-121 C.) can be prepared byboiling 2,5-bis- [4 N ethyl N n propyl amino phenyl (1')] 1,3,4-oxadiazole for ten hours with eight times its weight of formamide.The reaction product obtained is recrystallized from 70% ethyl alcohol.

2,5 bis [4' (N iso amyl amino) phenyl (1) 1,3,4-triazole correspondingto Formula 10 (melting point 130-13l C.) can be prepared by heating2,5-bis-[4-(N- iso-amyl-amino)-phenyl-( 1')]-1,3,4-oxadiazole, for tenhours with ten times its weight of formamide. The reaction product isboiled for one hour under reflux with 10% hydrochloric acid and, aftercooling, the reaction mixture containing hydrochloric acid isneutralized with sodium hydroxide. The precipitate that thereuponsettles out is separated by suction from the mother liquor andrecrystallized from ethyl alcohol.

2,5 bis [4' (N ethyl N acetyl amino) phenyl- (1')]-1,3,4-triazolecorresponding to Formula. 11 (melting point 128-130 C.) can be preparedby boiling 30 g. of the compound corresponding to Formula 4, for threehours with 250 g. of acetic anhydride. The reaction mixture is pouredinto water, the liquid is neutralized with ammonia and the resultingcolorless precipitate is recrystallized from 96% ethyl alcohol.

2,5 bis [4' N cyclohexyl amino phenyl (1')]- 1,3,4-triazole can beprepared by boiling 2,5-bis-[4-N-cyclohexyl-amino-phenyl-(l)]1,3,4-oxadiazole, for ten hours with tentimes its weight of formamide. When the reaction is complete, thereaction mixture is poured into water, and the precipitate is filteredand dried. The formyl compound resulting from boiling with formamide ishydrolyzed by boiling for two hours with 10% hydrochloric acid. Aftercooling, the hydrochloride solution is neutralized with ammonia and theN-cyclohexylamino compound precipitates out. It is recrystallized from96% ethyl alcohol.

Embodiments of the invention by way of example and methods of producingthe same will now be set forth in the following specific examples:

Example 1 1 g. of the compound corresponding to Formula 6 and 1 g. ofcolophony formaldehyde resin (e.g. the product marketed under theregistered trademark Corepal by Farbenfabriken Bayer A.G., Leverkusen)are dissolved in 30 g. of benzene; the solution is applied to paper, thesurface of which has been pretreated against the penetration of organicsolvents, and the paper then dried.

With the paper thus coated a direct positive image can be produced bythe electrophotographic process by providing the dry coating on thepaper with a positive electric charge by means of a corona dischargeexposed under a positive master to the light of a high-pressure mercurylamp, and then dusting over with resin powder colored with carbon blackin manner known per se. A positive image is formed, which can be fixedby slight heating to produce a permanent image having excellentcontrast. The background of the paper is brightened by the substancecoated thereon.

If in the above-described process a transparent support, such as acellulose acetate foil, is used instead of paper, an electrophotographicpositive image produced thereon can be used as a master for furtherreproduction on light-sensitive sheets.

Example 2 1 g. of the compound corresponding to Formula 2 and 2 g. ofcoumarone resin (e.g. the coumarone resin 701/70 produced by theGesellschaft fiir Teerverwertung, Duisburg-Meiderich) are dissolved in30 g. of methylene chloride and the solution is applied to an aluminiumfoil. After evaporation of the solvent, a coating is left on the surfaceof the foil adhering firmly thereto.

With the thus-coated aluminium foil, images can be produced from mastersby the electrophotographic process in known manner per se, and paperprints with good contrast can be obtained therefrom by the transferprocess.

Example 3 0.5 g. of the compound corresponding to Formula 1, 1.5 g. ofthe compound corresponding to Formula 3 and 1 g. of the synthetic resinknown as Kunstharz AW-2 (produced by Badische Anilinund Soda-FabrikA.G.,

' 9 Ludwigshafen am Rhein) are dissolved in 50 g. of benzene and thesolution is applied to a paper prepared in accordance with U8. Patents2,534,650, 2,681,617 or 2,559,610. After evaporation of the solvent acoating is left which adheres firmly to the surface of the foil. In theelectrophotographic process, direct positive images with good contrastare produced from masters with this coated paper. After being fixed byheating these images can be converted into a printing plate, if thepaper is wiped over with 96% ethyl alcohol, rinsed well with water andrubbed with greasy ink in the presence of 1% phosphoric acid. Positiveprinting plates are obtained which can be set up in an offset machineand used for printing.

Example 4 0.5 g. of the compound corresponding to Formula 4, 1 g. of thecompound corresponding to Formula 2 and 1 g. of resin-modified maleicacid resin (e.g. the product marketed under the trade name BeckaciteK-125 by Reichhold Chemie A.G., Hamburg) are dissolved in 30 g. ofbenzene and applied to a superficially-roughened aluminium foil. Afterevaporation of the solvent, a coating is left which adheres firmly tothesurface of the foil. Subsequent procedure is as described in Example 1;after the powder image has been fixed a positive image is obtained onthe aluminium foil. This image can be converted into a printing plate byapplying to the aluminium foil a 50% acetic acid solution, rinsing withwater and then rubbing in 1% phosphoric acid and greasy ink. A positiveprinting plate is obtained, which can be set up in an offset machine andused for printing.

Example 5 1 g. of the compound corresponding to Formula 5, 1 g. of aphenol-formaldehyde resin modified with colophony (e.g. the resinproduced by polycondensation and marketed under the registered trademarkRhenophen, by Rheinpreussen G.m.b.H., Homberg (Ndrh.)) and 0.01 g. ofVictoria blue B are dissolved in 30 g. of benzene. This solution isapplied to a paper which is light-permeable, but not transparent, andthe surface of which has been pretreated against the penetration oforganic solvents, and the paper is then dried. The product Rhenophen isdescribed on page 32 of the German publication "Lackrohstoff-Tabellen,by Erich Karsten (1955).

After the paper has been positively charged by means of a coronadischarge, it is placed, coated side down, on a page of a book which maybe printed on both sides, and exposed for two seconds to the light of a100-watt incandescent lamp. Exposure takes place through the back of thelight-permeable, but not transparent paper, a sheet of black paper beingplaced against the back of the page.

After exposure, the image formed on the light-permeable, but nottransparent paper foil is developed by dusting over with a carbonblack-resin powder, and a positive mirror-image with very good contrastis obtained. It can be transferred by pressure to a suitable paper or toa plastic foil to form a correct image. The correct image can also beproduced by means of an electric field in manner known per se. If thepaper or plastic foil is transparent, this image can be used as anintermediate original for further reproduction, for example, onphotoprinting paper.

Example 6 The procedure as in Example 1 is followed except that thecoating solution used consists of 1 g. of the compound corresponding toFormula 7, 0.03 g. of rhodamine 6G and 1 g. of ketone formaldehyde resin(e.-g. that known as Kunstharz EM, produced by polycondensation byRheinpreussen G.m.b.H., Homberg (Ndrh.)), in 30 g. of glycol monomethylether. Positive images with good contrast are obtained inelectrophotographic image production. By episcopic projection, imagescan be pro- 10 duced also from pages printed on both sides. Half andwhole tones are reproduced with good contrast. The product Kunstharz EMis described on page of Lackrohstoff-Tabellen.

Example 7 The procedure as in Example 1 is followed except that thecoating solution used consists of 0.5 g. of the compound correspondingto Formula 2 and 0.5 g. of the compound corresponding to Formula 6 in 30g. of glycol monomethyl ether. Positive images with very good contrastare obtained in electrophotographic image production.

Example 8 2 g. of the compound corresponding to Formula 8 are dissolvedin 30 cc. of glycol monomethyl ether and the solution applied to analuminium foil. Evaporation of the solvent leaves a coating whichadheres firmly to the surface of the foil. Subsequent procedure is asdescribed in Example 1, whereby a positive image is obtained on thealuminium foil when the electrophotographically-produced image has beendusted over with resin and fixed by heat or treated withtrichloro-ethylene vapor. The image-bearing aluminium foil can beconverted into a printing plate, by wiping over the image side of thefoil a 96% ethyl alcohol solution, rinsing with water and rubbing withgreasy ink and 1% phosphoric acid. A positive printing plate is obtainedwhich may be set up in an offset machine and used for printing.

Example 9 1 g. of the compound corresponding to Formula 9 and 1 g. ofthe compound corresponding to Formula 10 are dissolved in a mixture of20 cc. of glycol monomethyl ether and 10 cc. of benzene and the solutionis applied to transparent paper foil the sunface of which has beenpretreated against penetration of organic solvents, and the paper isthen dried. By an electrophotographic process, images with good contrastare produced on this coated transparent paper, which images can be fixedby heat or by treatment with trichloroethylene vapor. The product canthen be used as an intermediate original for further reproduction, e.g.for photoprinting on sensitized paper.

Example 10 The procedure as in Example 1 is followed except that thecoating solution consists of 2 g. of the compound corresponding toFormula 2 in 30 cc. of glycol monomethyl ether. Positive images withvery good contrast are obtained by an electrophotographic process asheretofore described.

Example 11 The procedure as in Example 1 is followed, except that thecoating solution consists of 1 g. of the compound corresponding toFormula 11 and 1 g. of colophony in 30 g. of glycol monomethyl e ther.Positive images are obtained by an electrophotographic process asheretofore described.

Example 12 1 g. of the compound corresponding to Formula 2, '1 g. of aresin modified with zinc (for example Zinkresinat 357, a productprepared by Lehmann & Crebert, Mannheim-Rheinau), and 0.02 g. of acidviolet 6BN are dissolved in 30 g. of benzene. The solution is applied topaper and dried. After being negatively charged by means of a coronadischarge, the paper is exposed for A second under a positive master tothe light of a 100-watt incandescent lamp at a distance of about 15 cm.and dusted with a resin powder colored with carbon black as inExample 1. A positive image appears which is fixed by heat. The productZinkresinat 357 is described on page 25 of Lackrohstofl-Tabellen.

1 1 Example 13 The procedure as in Example 1 is followed, except thatthe coating solution is prepared with 30 g. of glycol monomethyl ethercontaining 1 g. of the compound corresponding to Formula 9 and 1 g. ofpartly polymerized natural resin (e.g. the natural resin about 40%polymerized marketed by the American firm Hercules Powder Company,Wilmington, under the trade name Hercules Poly Pale resin). Positiveimages are obtained. The product Poly Pale is described on page 24 ofLackrohstoff-Tabellen.

Instead of Hercules Poly Pale, a resin that is about 80% dimerizedabietic acid (for example, that marketed by the same American firm underthe trade name Hercules Dymerex) can be used, or a hydrated resin, suchas the resin produced as a mixture of dihydro and tetrahydro-abieticacid by the Hercules Powder Company and marketed under the trade nameHercules Staybelite. The product Dymerex is described on page 24 ofLackrohstoif-Tabellen.

Example 14 A paper base is coated with a solution in 100 g. of acetoneof g. of a product prepared by after-chlorination of polyvinyl chloride(such as the material marketed by Dynamit A. G., Rheinfelden, under theregistered trademark Rhenofiex). The coated solution is dried. Whendried, the coated paper is further coated with a solution of 1 g. of thecompound corresponding to Formula 2 and 1 g. of ketone resin (such asthat known as Kunstharz AP, marketed by Chemische Werke HulsAktiengesellschaft, Marl), in 30 g. of glycol monomethyl ether and againdried. The paper is then further processed as in Example 1 and gives animage with very good contrast even after one-second exposure under amaster to the light of a 100-watt incandescent lamp at a distance ofabout 15 cm.

Example 15 l g. of the compound corresponding to Formula 12 and 1 g. ofa resin modified with zinc (e.g. that marketed by Robert Kraemer,Bremen, under the trade name Erkazit Zinkharz 165) are dissolved in g.of benzene. The solution is coated on to paper and dried. The coatedpaper is further processed as described in Example 1. A positive imageis formed which is fixed by steam treatment. The product ErkazitZinkharz 165 is described on page 24 of Lackrohstolt-Tabellen.

Example 16 1 g. of the compound corresponding to Formula 2, l g. ofketone formaldehyde resin (e.g. the product marketed by the ChemischeWerke Huls A.G., Marl, under the trade name Kunstharz SK), and 0.03 g.of rhodamine B are dissolved in 30 g. of glycol monomethyl ether. Thesolution is coated onto paper and dried. In the electrophotographicprocess this paper, which after coating is pink in color, can be usedfor the production of direct positive images. After the coated paper hasbeen positively charged by means of a corona discharge, it is exposedunder a film diapositive, e.g. to a 100 watt incandescent lamp at adistance of about 15 cm. for /2 second, and dusted with resin powdercolored with carbon black in manner known per se. The positive imageformed is fixed by slight heating. It is characterized by excellentcontrast, the background having become practically colorless after theheating. If the rhodamine B is omitted from the coating solution, otherconditions being the same, the positively charged paper has to beexposed under the master for 6 seconds. The product Kunstharz SK isdescribed on page 80 of Lackrohstotf-Tabellen."

Example 17 10 g. of after-chlorinated polyvinyl chloride, e.g. theproduct marketed by Dynamit Aktiengesellschaft vormals Alfred Nobel &Co., Troisderf, Werk Rheinfelden, under the registered trademarkRhenofiex, are dissolved in g. of methyl-ethyl-ketone. To this solutionare added first 10 g. of the compound corresponding to Formula 12 in 50g. of toluene and then 0.01 1 g. of rhodamine B extra (Schultz,Farbstofftabellen, 7th edition, 1st vol. (1931), No. 864) dissolved in 2g. of methyl alcohol. With the solution thus obtained, which has akinetic viscosity of about 20.8 centistokes (17.1 centipoises), paper.is machine coated by means of a cast-coating device. The thickness ofthe coating obtained is about 6 microns. On this paper direct positiveimages are pro duced by the electrophotographic process in the mannerdescribed in Example 1. Light-sensitivity is very great. Fromdouble-sided printed sheets images very rich in contrast can be producedepiscopically with an exposure of 1 second to alight of about 30 lux.

The compound corresponding to Formula 12 is produced when 20 g. of2-[4'-diethyl-amino-phenyl-(l)]-5- [4"-dimethyl amino-phenyl-(1")] 1,3,4oxadiazole are heated with 200 g. of formamide for 10 hours at C. Afterthe reaction mixture has been cooled, it is poured into water, and thereaction product is separated by suction and recrystallized from 80%ethyl alcohol.

Example 18 10 g. of a product prepared by after-chlorination ofpolyvinyl chloride, e.g. the plastic marketed by DynamitAktiengesellschatt, Rheinfelden, under the registered trademarkRhenofiex, are dissolved in 100 g. of methylethyl-ketone. To thissolution there are added first a solution of 10 g. of the compoundcorresponding to Formula 2 in 50 g. of toluene and then a solution of0.004 g. of ethyl violet (Schultz, Farbstofitabellen, 7th edition, 1stvol. (1931), No. 787) in 2 g. of methyl alcohol. With the solution thusobtained, which has a kinetic viscosity of approximately 20.8centistokes (17.1 centipoises) a paper base is machine coated. Thethickness of the coating should, for favorable results, be about 6microns. After the coating has been dried the paper is negativelycharged by means of a corona discharge and then a latent image isproduced episcopically on this paper from a double-sided printed Page.The paper is now treated on its coated side with a developer consistingof small glass balls and a finely divided mixture of resin and carbonblack; The black colored resin adheres to the parts of the layer notstruck by light during exposure and a positive image becomes visible;this is slightly heated and thereby made permanent (fixed). It showsgood contrast.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A 2,5-bis-(p-aminophenyl)-1,3,4-triazole.

2. A compound having the formula in which R, R R and R are selected fromthe group consisting of hydrogen, alkyl, cycloalkyl, and acyl radicals,and R is selected from the group consisting of hydrogen and alkylradicals.

3. A compound having the formula I It.

in which R is selected from the group consisting of hydrogen and loweralkyl.

4. A compound having the formula layer, the latter containing a compoundhaving the formula in which R, R R and R are selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, and acyl radicals, and R isselected from the group consisting of hydrogen and alkyl radicals.

9. An electrophotographic material according to claim 8 in which thephotoconductive layer contains a dyestuff sensitizer.

10. An electrophotographic material according to claim 4 in which thephotoconductive layer contains an organic colloid.

111. An electrophotograph-ic material comprising a conductive supportlayer and a photoconductive insulating layer, the latter containing acompound having the formula in which R is selected from the groupconsisting of hydrogen and lower alkyl.

12. An electrophotog-naphic material according to claim 4 in which thephotoconductive layer contains a dyestuff sensitizer.

13. An electrophotographic material according to claim 11 in which thephotoconductive layer contains an organic colloid.

14. An electrophotographic material comprising a conductive supportlayer and a photoconductive insulating I layer, the latter containing acompound having the formula in which R, R R and R are lower alkylradicals, and R is selected from the group consisting of hydrogen andlower alkyl radicals.

15. An electrophotographic material according to claim 14 in which thephotoconductive layer contains a dyestuff sensitizer.

16. An electrophotographic material according to claim 14 in which thephotoconductive layer contains an organic colloid.

17. A process according to claim 37 in which the photoconductive layercontains a dyestulf sensitizer.

18. A process according to claim 37 in which the photoconductive layercontains an organic colloid.

19. A process according to claim 38 in which the photoconductive layercontains a dyestulf sensitizer.

20. A process according to claim 38 in which the photoconductive layercontains an organic colloid.

21. A process according to claim 39 in which the photoconductive layercontains a dyestuff sensitizer.

22. A process according to claim 39 in which the photoconductive layercontains an organic colloid.

23. A process according to claim 40 in which the photoconductive layercontains a dyestufi' sensitizer.

24. A process according to claim 40 in which the photoconductive layercontains an organic colloid.

25. A compound having a formula 1H1 N HzN- -o (LO-N112 N H 26. Acompound having a formula H502 --N C2155 II II /N 0\ /c N\ 1515C: N 01HH 27. A compound having a formula H3O NN CH3 C: -C H30 N \CH} H 28. Acompound having a formula v H\ H C H502 N CzH5 H 29. A compound having aformula HsC\ CH: aQ-a AC H3O N \CH3 30. A compound having a formula sCzC3115 -CW rncg \N/ onn 31. A compound having a formula H\ NN H -Qa a0HaCOC I}; COOHa 37. A photographic reproduction process which comprisesexposing an electrically charged, supported photoconductive insulatinglayer to light under a master and developing the resulting image, thephotoconductive layer comprising a2,5-bis-(p-aminophenyl)-1,3,4-triazole.

38. A photographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula in whichR, R R and R are lower alkyl radicals, and

R is selected from the group consisting of hydrogen and lower alkylradicals.

39. A photographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula NN II IIin which R is selected from the group consisting of hydrogen and loweralkyl radicals.

40. A photographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula in whichR, R R and R are lower a-lkyl radicals and R is selected from the groupconsisting of hydrogen and lower alkyl radicals.

41. A photographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula 42. Aphotographic reproduction process which comprises exposing anelectrically charged, supported photoconductive rnsulating layer tolight under a master and 16 developing the resulting image, thephotoconductive layer comprising a compound having the formula 43. Aphotographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula 113 C CIi;

44. A photographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula 45. Aphotographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula 46. Aphotographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula 47. Aphotographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula ii H CCH1000 00cm 48. A photographic reproduction process which comprisesexposing an electrically charged, supported photoconductive insulatinglayer to light under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula 49. Aphotographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula 51. Aphotographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and developing the resulting image, thephotoconductive layer comprising a compound having the formula 52. Aphotographic reproduction process which comprises exposing anelectrically charged, supported photoconductive insulating layer tolight under a master and 18 developing the resulting image, thephotoconductive layer comprising a compound having the formulaReferences Cited in the file of this patent UNITED STATES PATENTS2,297,691 Carlson Oct. 6, 1942 2,663,636 Middleton Dec. 22, 19532,692,178 Grandadam Oct. 19, 1954 2,765,304 Siegrist et al. Oct. 2, 19562,803,542 Ullrich Aug. 20, 1957 2,809,294 Vyverberg Oct. 8, 19572,817,665 Zweidler et a1 Dec. 24, 1957 2,825,814 Walkup Mar. 4, 19582,852,525 Petersen et a1. Sept. 16, 1958 FOREIGN PATENTS 201,416Australia Apr. 13, 1956 396,778 Great Britain Aug. 11, 1933 OTHERREFERENCES Winslow et al.: Jour. Amer. Chem. Soc., vol. 77, pp.4751-4756 (September 1955). (Copy in Sci. Library.)

37. A PHOTOGRAPHIC REPRODUCTION PROCESS WHICH COMPRISES EXPOSING ANELECTRICALLY CHARGED, SUPPORTED PHOTOCONDUCTIVE INSULATING LAYER TOLIGHT UNDER A MASTER AND DEVELOPING THE RESULTING IMAGE, THEPHOTOCONDUCTIVE LAYER COMPRISING A2,5-BIS-(P-AMINOPHENYL)-1,3,4-TRIAZOLE.